Farm exposure in utero may protect against asthma, hay fever and eczema

Abstract

The aim of the present study was to assess which factors contribute to the lower prevalence of allergic diseases in farmers' children, and the importance of timing of exposure.In a cross-sectional questionnaire survey, asthma symptoms, hay fever and eczema were assessed, as well as current, early and prenatal farm-related exposures in 1,333 farmers' children and 566 reference children aged 5-17 yrs.Farmers' children had a lower incidence of asthma symptoms and eczema. Current and maternal exposure during pregnancy to animals and/or grain and hay reduced the risk of asthma symptoms, hay fever and eczema. The exposure-response association for maternal exposure was nonlinear for most outcomes. After mutual adjustment, the effects of prenatal exposure remained unchanged whereas current exposure remained protective only for asthma medication, asthma ever and hay fever. Exposure during the first 2 yrs was not associated with symptoms, after controlling for prenatal exposure. A combination of prenatal and current exposure was most strongly associated with wheeze (odds ratio ( Prenatal exposure may contribute to the low prevalence of asthma, hay fever and eczema in farmers' children, but continued exposure may be required to maintain optimal protection.

Protective effects of farming on allergies and asthma: have we learnt anything since 1873?

“…The aforementioned study by Ege et al in farmers' children showed that both atopic sensitization and gene expression of TLR2, TLR4 and CD14 were strongly associated with prenatal exposures [47]. Similarly, we showed that exposure of the mother to farm animals during pregnancy was strongly associated with a subsequent reduced prevalence of hayfever, asthma and eczema [20]. The importance of prenatal exposures has also been confirmed in animal models of asthma [70].…”

“…The observed protective effects of farming on allergies and asthma have been particularly strong for animal contact [5,10,11,13,15,20]. Farm animals are associated with high exposures to microorganisms, in particular bacterial endotoxin [45].…”

“…A related issue is that a number of studies have found consistently low prevalences of allergies and asthma in farmers' children, both in high-income countries such as Canada, the USA, Australia, New Zealand and Europe [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and in lowincome countries including Mongolia and Southern Africa [21,22]. These protective effects for allergies and asthma have also been observed in adult farmers [23][24][25][26][27][28][29][30][31][32][33][34][35][36], despite the increased risks of other respiratory conditions, such as chronic obstructive pulmonary disease, reduced lung function and farmers' lung [37].…”

Regulatory B Cells - Implications in Autoimmune and Allergic Disorders

“…A relationship between helminth infections and protection against hyperinflammatory disorders has also been established in various mouse models for food allergy (Nagler-Anderson 2006), asthma (Smits, Hammad et al 2007;Amu, Saunders et al 2010), T1D (Zaccone, Fehervari et al 2003;Liu, Sundar et al 2009), CIA (Osada, Shimizu et al 2009) and EAE (La Flamme, Ruddenklau et al 2003;Wilson, Taylor et al 2010). Furthermore, different cross-sectional studies show that children living in farming environments are protected from childhood asthma and atopy and this correlation has been attributed to contact with livestock (Ege, Frei et al 2007) and hay and the consumption of raw cow's milk (Douwes, Cheng et al 2008;Loss, Apprich et al 2011). In farming environments, both outdoor and indoor microbial exposure are higher and more diverse compared to nonfarming environments (von Mutius, Braun-Fahrlander et al 2000;Ege, Mayer et al 2011).…”

Asthma phenotyping, therapy, and prevention: what can we learn from systems biology?

“…Ege et al found that maternal exposure to a farming environment during pregnancy increased atopic sensitization of the offspring (27), suggesting a role for intrauterine and epigenetic mechanisms. A European cross-sectional questionnaire survey also showed that maternal exposure to a farm environment during pregnancy had a protective effect against asthma and hay fever in the offspring (28). In general, a very tight interaction has been shown to exist between maternal trans-placental signals and the fetal immune system; for instance, maternal cells cross the placental barrier, settle in the offspring's lymph nodes until early adulthood, and suppress anti-maternal immune reactions by induction of fetal regulatory T cells (29).…”